Person to Person in Japan

While still in the midst of their study abroad experiences, students at Linfield College write reflective essays. Their essays address issues of cultural similarity and difference, compare lifestyles, mores, norms, and habits between their host countries and home, and examine changes in perceptions about their host countries and the United States. In this essay, Stacey Strovink describes her observations during her study abroad program at Kanto Gakuin University in Yokohama, Japan

Fruits, Flowers, and Foam Wars

Postcard from Stacey Strovink, during the Linfield College Semester Abroad Program at the Universidad San Francisco de Quito in Ecuado

Solidarity Has No Color

Postcard from Stacey Strovink, during the Linfield College Semester Abroad Program at the Universidad San Francisco de Quito in Ecuado

Go Go Go

Postcard from Stacey Strovink, during the Linfield College Semester Abroad Program at Kanto Gakuin University in Yokohama, Japa

Diversity of Decline-Rate-Corrected Type Ia Supernova Rise Times: One Mode or Two?

B-band light-curve rise times for eight unusually well-observed nearby Type Ia supernovae (SNe) are fitted by a newly developed template-building algorithm, using light-curve functions that are smooth, flexible, and free of potential bias from externally derived templates and other prior assumptions. From the available literature, photometric BVRI data collected over many months, including the earliest points, are reconciled, combined, and fitted to a unique time of explosion for each SN. On average, after they are corrected for light-curve decline rate, three SNe rise in 18.81 +- 0.36 days, while five SNe rise in 16.64 +- 0.21 days. If all eight SNe are sampled from a single parent population (a hypothesis not favored by statistical tests), the rms intrinsic scatter of the decline-rate-corrected SN rise time is 0.96 +0.52 -0.25 days -- a first measurement of this dispersion. The corresponding global mean rise time is 17.44 +- 0.39 days, where the uncertainty is dominated by intrinsic variance. This value is ~2 days shorter than two published averages that nominally are twice as precise, though also based on small samples. When comparing high-z to low-z SN luminosities for determining cosmological parameters, bias can be introduced by use of a light-curve template with an unrealistic rise time. If the period over which light curves are sampled depends on z in a manner typical of current search and measurement strategies, a two-day discrepancy in template rise time can bias the luminosity comparison by ~0.03 magnitudes.Comment: As accepted by The Astrophysical Journal; 15 pages, 6 figures, 2 tables. Explanatory material rearranged and enhanced; Fig. 4 reformatte

Multiscale Technicolor and Top Production

Pair-production of heavy top quarks at the Tevatron Collider is significantly enhanced by the color--octet technipion, $\eta_T$, occurring in multiscale models of walking technicolor. We discuss $\bar tt$ rates for $m_t = 170$ GeV and $M_{\eta_T} = 400-500$ GeV. Multiscale models also have color--octet technirho states in the mass range 200-600 GeV that appear as resonances in dijet production and technipion pair--production.Comment: 12 pages (plain TeX) and 4 figures (uuencoded), FERMILAB--PUB--94/007-T and BUHEP-94-

Implications of Two Type Ia Supernova Populations for Cosmological Measurements

Recent work suggests that Type Ia supernovae (SNe) are composed of two distinct populations: prompt and delayed. By explicitly incorporating properties of host galaxies, it may be possible to target and eliminate systematic differences between these two putative populations. However, any resulting {\em post}-calibration shift in luminosity between the components will cause a redshift-dependent systematic shift in the Hubble diagram. Utilizing an existing sample of 192 SNe Ia, we find that the average luminosity difference between prompt and delayed SNe is constrained to be $(4.5 \pm 8.9)$. If the absolute difference between the two populations is 0.025 mag, and this is ignored when fitting for cosmological parameters, then the dark energy equation of state (EOS) determined from a sample of 2300 SNe Ia is biased at $\sim1\sigma$. By incorporating the possibility of a two-population systematic, this bias can be eliminated. However, assuming no prior on the strength of the two-population effect, the uncertainty in the best-fit EOS is increased by a factor of 2.5, when compared to the equivalent sample with no underlying two-population systematic. To avoid introducing a bias in the EOS parameters, or significantly degrading the measurement accuracy, it is necessary to control the post-calibration luminosity difference between prompt and delayed SN populations to better than 0.025 mag.Comment: 4 pages, 4 figures; New figures added, some old figures removed; The effect of the uncertainty in the two population model on parameter estimation discussed; Reflects version accepted for publication in Astrophys. J. Let

Nonlinear Decline-Rate Dependence and Intrinsic Variation of Type Ia Supernova Luminosities

Published B and V fluxes from nearby Type Ia supernovae are fitted to light-curve templates with 4-6 adjustable parameters. Separately, B magnitudes from the same sample are fitted to a linear dependence on B-V color within a post-maximum time window prescribed by the CMAGIC method. These fits yield two independent SN magnitude estimates B_max and B_BV. Their difference varies systematically with decline rate Delta m_15 in a form that is compatible with a bilinear but not a linear dependence; a nonlinear form likely describes the decline-rate dependence of B_max itself. A Hubble fit to the average of B_max and B_BV requires a systematic correction for observed B-V color that can be described by a linear coefficient R = 2.59 +- 0.24, well below the coefficient R_B ~ 4.1 commonly used to characterize the effects of Milky Way dust. At 99.9% confidence the data reject a simple model in which no color correction is required for SNe that are clustered at the blue end of their observed color distribution. After systematic corrections are performed, B_max and B_BV exhibit mutual rms intrinsic variation equal to 0.074 +- 0.019 mag, of which at least an equal share likely belongs to B_BV. SN magnitudes measured using maximum-luminosity or CMAGIC methods show comparable rms deviations of order ~ 0.14 mag from the Hubble line. The same fit also establishes a 95% confidence upper limit of 486 km/s on the rms peculiar velocity of nearby SNe relative to the Hubble flow.Comment: 21 pages, 11 figures, 10 tables, to appear in The Astrophysical Journal, uses emulateapj_051214.cl